Circuit breakers are utilized throughout electrical power distribution networks for protecting the networks from damage caused by, for example, overload or short circuits. The circuit breaker is operated by a drive system effectuating the opening and closing of the circuit breaker. The circuit breaker has to be opened (tripped) quickly upon detection of a fault, and this in turn puts high demands on the drive system for operating the circuit breaker. The opening and closing of contacts of the circuit breaker should be performed rapidly and reliably.
An example of such drive system includes a mechanical spring. The energy stored in the spring is released and utilized for opening the circuit breaker contact members.
International Patent Publication WO 2005/024877 discloses another example of such drive system for operating a circuit breaker. The drive system includes, for example, an electric motor energized by a drive circuit having electronics such as capacitor banks and thyristors.
Although this can be an acceptable solution, the thyristors and related electronic components make it a rather costly one. It would therefore be desirable to provide alternatives for operating circuit breakers, which can be less expensive.
Another drive system using an electric motor is described in GB2226453. In this document there is provided an electromagnetic switch drive having a switch drive shaft which is connected to a switching member which is rotatable between two switch positions. A bar-shaped two-pole permanent magnet is rotationally rigidly mounted on the switch drive shaft. The magnet is magnetised at right angles to the switch drive shaft and capable of being turned by the magnetic field of a pole-reversible DC voltage-operated coil between two extreme positions defined by abutments. In the document these abutments are described as being placed for limiting the angle of rotation of the permanent magnet to a maximum of 60 on either side of the transverse axis of the coil which defines a midway position.
U.S. Pat. No. 4,227,164 describes a rotary solenoid or similar electromagnetic rotating apparatus that is capable of smoothly rotating through an angular range of approximately 180 degrees, in both directions, without employing a return spring or other similar device.
U.S. Pat. No. 4,795,929 describes a rotary actuator in which there is a freely rotatable permanent magnetic armature between two stators. At least one of the stators produces an asymmetrical magnetic flux field that acts upon the magnetic field of the armature to cause the same to rotate.
EP0800195 describes a drive system for driving a circuit breaker using a relay.